Brake assembly



Mar h 13, 93 c. A. SAWTELLE El AL BRAKE AS SEMBLY Filed May 26, 1930 INVENTORS awzzZZe C/ iard as /f. S firm a7? fl Farms flag 526) WWW MW ATTORNEYS Patented Mar. 13, 1934 1TB s'rss- P FFICE'.

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BRAKE ASSEMBLY Michigan Application May 26, 1936, Serial No. 455,873

9 Claims.

The invention relates to brake assemblies of that type comprising a brake drum and an internal flexible band braking element together with mechanism for expanding said element into friction contact with the drum. It is the object or" the invention to obtain a simple construction which is equally eiiective in braking when running forward or in reverse. It is a further object to obtain a construction which to some extent is self-energizing and in both forward and reverse directions, and still further it an object to obtain various advantages as hereinafter set forth.

In the drawing:

Figure l is an elevation of my improved assembly;

Figure 2 is a cross section on line 22 of Figure l.

illustrated, is the brake drum and B an internal flexible brake band which extends around the greater portion of the circumference of the driun. This band is reinforced by a rib flange C which is of greatest depth in the center of the band and tapers therefrom toward the opposite ends.

It is usuai with such constructions to rigidly attach to each end of the band an eye bracket to which the levers or linkage for expanding the band are pivotally attached. This, however, necessitates the transmission of any force applied to eyes around through the band which being flexible has a tendency to buckle. To avoid this objection as well as to secure other advantages, E have substituted for the rigidly attached eye, brace members which form chords of arcs or segments of the band, together with abutments on the band for engaging the opposite ends of said braces. The actuating mechanism is attached to these braces at points therein near the ends of the band, but the force applied is distributed thro' the brace to both ends thereof and the portions of the band adjacent thereto. This construction has a number of advantages, which will be described in detail.

As shown, D and E are the brace members engaging the opposite ends of the band and F F G G are abutment members secured to' the band and engaging opposite ends of the braces. These members F F G G are riveted or otherwise secured to the band and are provided with flanges H which overlap toe portions I at the ends of the brace thereby retaining the brace in position without direct attachment between the same and the band. Thus any force applied to the brace in an endwise direction will be transmitted to the band through the abutments at one end only and the segment of band between the opposite abutments is free to flex into conformity with the brake drum without restraint from the brace.

As has been stated, it is one of the objects of the invention to obtain a construction which is to some extent self-energizing and operative in this manner in both forward and reverse rotations of the drum. It is equally important to avoid any tendency to grab or seize independent of the controlling force. Both of these effects are due to the so-called wrapping action which is strongest in the portion of the band which is farthest removed from the anchorage in the direction counter to the rotation of the drum. If, however, the direction of rotation is reversed without change in anchorage, there will be an unwrapping tendency in the portion previously having the strongest wrapping tendency. Therefore, to obtain the desired result a linkage is provided between the levers for actuating the opposite ends of the band through which both the wrapping ends and the unwrapping ends are simultaneously actuated towards and from the drum but with a preponderance of leverage in favor of the wrapping force. ihis mechanism as shown comprises a bell crank lever J fulcrumed on the pivot K mounted on the brake head L and the bell crank lever M fulcrumed on the pivot N on said brake head. The bell crank J has its arm J pivotally connected to-the eye D of the brace D. The bell crank M has an arm M pivotally attached to the eye E of the brace E. There is also a long lever arm M on the bell crank M which pivotally and slidably engages a short arm J on the bell crank lever J. This pivotal and sliding engagement is provided by a knuckle O which pivots in the member J and is recessed for sliding engagement with the arm N Thus when the drum is moved in its forward direction the wrapping force operating through the bell crank levers J and M will by reason of the step-up leverage be in excess of the unwrapping force so that the brake will be self-energized. On the other hand, if the direction of the drum is reversed, then with the construction as thus far described, the wrapping force would be less than the unwrapping force, not only losing the self-energizing feature but requiring additional manual force to overcome the unwrapping tendency.

To render the construction self-energizing in both directions of rotation of the drum and also to further assist in preventing seizure or chattering, the brake is provided with the braces previously described and the brace D which is on the wrapping portion of the band in the forward direction of rotation of the drum, is longer than the brace E which is on the unwrapping portion. When the drum is rotating in the forward direction, the abutment F bearing on the brace D will transmit the wrapping force through the levers J and M as previously described. However, on reverse rotation, the transmission of force between the brake band and the brace D is by way of the abutment F and the acute angular relation between the brace D and the bell crank arm J compensates for the unequal length of the arms J and M so that the wrapping force is still in preponderance over the unwrapping force. To permit the band segment between the abutments G and G to go into full contact with the drum when in reverse a clearance is provided between the abutment G and the adjacent end of the brace E. This allows sufficient independent movement of the band to insure full wrapping contact.

The brake may be operated and controlled by any suitable means but as shown a hydraulic unit P is interposed between the eyes. D and E., Springs Q connected to the band and to anchor posts R serve to retract the brake from contact with the drum and a suitable guide member S engages the central portion of the band to hold the same in concentric relation to the drum.

In operation, if the brake: drum is rotating in the forward direction as indicated by the full arrow, the band is expanded by the full operation of the unit P. This will bring the outer surface of the entire band into frictional contact with the drum. The segment adjacent to the brace member D will be subjected to the strongest wrapping action, but as this segment is connected through the levers J and M to the brace E, the unwrapping portion of the brake will be held in frictional contact with the drum so as to practically equalize the braking effect all around the band. Furthermore, the brake is self-energizing by reason of the increase in power transmitted through the levers J and M. When the brake drum is revolving in reverse direction indicated by the dotted arrow, there will still be a preponderance of pressure derived from the wrapping portion'of the band which in this instance is that adjacent to the brace E, which pressure is applied through the brace D and abutment F to the portion of the band adjacent thereto. The result is that the brake isself-energized in both directions of rotation while in neither direction is there any tendency to seize or to chatter.

7 To provide for slight inaccuracies in construction or assembly, the brace bars D and E are preferably provided with flexible portions T between the eye portions and the adjacent end of the bar capable of yielding to compensate for such inequalities.

What we claim as our invention is:

1. The combination with a brake drum and a flexible internal brake band therein, of means for expanding said band into braking contact with the drum including a brace arranged as a chord across a segment of said band, and abutments secured to said band for slidably engaging opposite ends of said brace, for the purpose set forth.

2. The combination with a brake drum and an internal flexible band brake therein, means for expanding said band into frictional contact with said drum including a brace extending as a chord across a segment of said band and abutments on said band freely engaging opposite ends of said brace.

3. The combination with a brake drum and an internal flexible brake band therein, of means for expanding said band into frictional cori tact with said drum including a pair of brace bars arranged as chords across segments of said band adjacent to the opposite ends thereof, and abutments secured to said band freely engaging opposite ends of said braces.

4. The combination with a brake drum and an internal flexible brake band therein, of means for expanding said band into frictional contact with said drum including a pair of brace bars arranged as chords across segments of said band adjacent to the opposite ends thereof, one of said brace bars being of greater length than the other, and abutments secured to said band for engaging the opposite ends of said brace bars.

5. The combination with a brake drum and an internal flexible brake band therein, of means for expanding said band into frictional contact with said drum including a pair of brace bars arranged as chords across segments of said band adjacent to the opposite ends thereof, said bars being of unequal length, abutments on said band for engaging opposite ends of said brace bars, an abutment for the shorter bar providing a limited clearance between the same and the end of the bar.

6. The combination with a brake drum and an internal flexible brake band therein, of a compound lever for moving the ends of said brake band oppositely to expand said band into frictional contact with the drum, a pair of brace bars for pivotally engaging said compound lever at opposite ends of the brake band, said bars being arranged as chords across segments of said band and being of different lengths, abutments upon said brake band for engaging the opposite ends of said bars, one of the abutments for the shorter bar providing a limited clearance between the same and the end of the bar, said compound lever having engaging arms of different length with the longer arm on the lever engaging the shorter bar.

'I. The combination with a brake drum and a flexible internal brake band therein, of a brace arranged as a chord across a segment of the band and having the opposite ends slidably engaging the inner surface of the band, abutments fixed to the band and slidably engageable with opposite ends of the brace to maintain the same in assembled relation with the band, and means connected to the brace for expanding the band into braking contact with the drum.

8. The combination with a brake drum and a flexible internal brake band therein, of a pair of brace bars arranged as chords across seg- 1 ments of the band and having their opposite end portions slidably engaging the inner surface of the band, abutments fixed to the inner surface of the band and slidably engaging opposite end portions of the bars for maintaining the latter in assembled relation with the band, and means connected to both of said brace bars for expanding the band into braking contact with the drum.

9. The combination with a brake drum and a flexible internal brake band therein, of a brace arranged as a chord across a segment of the band, abutments secured to the band and slidably engaging opposite ends of the brace for maintaining the latter in assembled relation with the band, and means connected to the brace for expanding the band into braking contact with the drum.

CHARLES A. SAWTELLE. ARMIN A. DARMSTAETTER. 

